1. Field of the Invention
The present invention relates to a turbo compressor, and more particularly, to a turbo compressor that is capable of effectively cooling a bearing which supports a rotational shaft.
2. Description of the Background Art
FIG. 1 is a sectional view of a turbo compressor in accordance with a conventional art.
As shown in FIG. 1, the conventional turbo compressor includes a casing 106 having a suction hole 102 for sucking a fluid from an outside and a discharge hole 104 for discharging the sucked fluid, and having a certain space; a driving unit 108 installed inside the casing 106 and generating a rotational force; a first compressing part 112 connected to the driving unit 108 by a rotational shaft 110 and first compressing fluid; and a second compressing part 114 for secondly compressing the fluid compressed by the first compressing part 112.
In the casing 106, a fluid chamber 120 for sucking a fluid through the suction hole is formed, a first support member 116 for rotatably supporting one end portion of the rotational shaft 110 is fixed at one side of the casing 106, and a second support member 118 for rotatably supporting the other end portion of the rotational shaft 110 is fixed at the other side of the casing 106.
The driving unit 108 includes a stator 122 fixed at an outer circumferential face of the casing 106 and receiving a power from an external source, and a rotor 124 fixed at a circumferential face of the rotational shaft 110 and being rotated by an interaction with the stator 122.
The first compressing part 112 includes a first impeller 126 connected to one end portion of the rotational shaft 110 and compressing the fluid by being rotated along with the rotational shaft 110; and a first cover member 132 in which the first impleller 126 is rotatably inserted, a first compression chamber 128 is connected to the discharge hole 104 of the main body, into which the fluid of the fluid chamber 120 is introduced and first compressed, and a transfer passage 130 is formed to discharge the compressed fluid.
The second compressing part 114 includes a second impeller 134 connected to the other end portion of the rotational shaft 110 and compressing the fluid by being rotated along with the rotational shaft 110; and a second cover member 140 in which the second impeller 134 is rotatably inserted, a second compression chamber 136 is formed connected to the transfer passage 130 into which the first compressed fluid is introduced and secondly compressed, and a discharge hole 138 is formed to externally discharge the compressed coolant.
A radial bearing 142 is inserted between the first support member 116 and the outer circumferential face of the rotational shaft 110 and between the second support member 118 and the outer circumferential face of the rotational shaft 110, to support a load working in a radial direction of the rotational shaft 110.
A bearing bush 144 is connected in a vertical direction to the rotational shaft at one side thereof. The bearing bush 144 is supplied by a thrust bearing 146 which supports a load working in an axial direction of the rotational shaft 110.
The thrust bearing 146 is installed between the first cover member 132 and the first support member 116, and a bearing chamber 148 is formed where the bearing bush 144 is rotatably positioned.
A sealing member 150 is inserted between the outer circumferential face of both end portions of the rotational shaft 110 and the first cover member 132, to prevent leakage of the fluid compressed in the first and the second compression chambers 128 and 136.
The operation of the turbo compressor in accordance with the conventional art constructed as described above will now be explained.
When the driving unit 108 is driven, the rotational shaft 110 is rotated. Then the first impeller 126 and the second impeller 134 connected to the rotational shaft 110 are rotated to perform a compressing operation of the fluid.
That is, the fluid is introduced into the fluid chamber 120 through the suction hole 102, and the fluid introduced into the fluid chamber 120 is introduced into the first compression chamber 128 through the discharge hole 104, first compressed according to the rotation of the first impeller 126 and then supplied to the transfer passage 130.
The fluid supplied to the transfer passage 130 is introduced into the second compression chamber 136, secondly compressed by the rotation of the second impeller 134 and then externally discharged through the discharge hole 138.
At this time, when the rotational shaft 110 is being rotation, a load working in a radial direction of the rotational shaft 110 is supported by the radial bearing 142.
Since the pressure in the first compression chamber 128 which compresses the fluid first is smaller than that of the second compression chamber 136, an axial-directional load works on the rotational shaft 110 due to the pressure difference between the first compression chamber 128 and the second compression chamber 136. Such axial-directional load is supported by the thrust bearing 146.
In this respect, since the rotational shaft 110 is rotated at a high speed, a temperature of the bearing chamber 148 with the thrust bearing 146 is inserted is increased and the thrust bearing 146 is degraded. Thus, in view of the performance of the whole system and in order to lengthen the life of the bearing, it is requisite to cool the thrust bearing 146 and maintain its temperature to below a certain level.
The conventional bearing cooling method is that, in designing a structure of the sealing member 150 inserted between the first cover member 132 and the rotational shaft 110, a certain leakage of fluid is allowed to occur, so that when the fluid which is first compressed after being introduced into the first compression chamber 128 is introduced into the bearing chamber 148 through the sealing member 150, thereby performing a cooling operation of the thrust bearing 146.
However, the conventional turbo compressor has a problem that the leakage amount of fluid supplied from the first compression chamber to the bearing chamber differs depending on a structure designing of the sealing member.
That is, if a small amount of fluid is leaked to the bearing chamber, the cooling operation of the thrust bearing is not smoothly performed, and thus, the temperature is increased according to the friction of the bearing. Then, a coating layer of the bearing is damaged, resulting in that the performance of the whole system is degraded, the durability of the bearing is shortened, and a reliability is degraded.
On the other hand, if a large amount of fluid is leaked to the bearing chamber, when the fluid is compressed, a large amount of fluid is leaked, resulting in that a compression efficiency of the compressor is degraded.
Therefore, an object of the present invention is to provide a turbo compressor that is capable of smoothly performing a cooling operation of a bearing without degrading a compression performance of a compressor in such a manner that when a temperature of a bearing chamber with a thrust bearing inserted therein increases, a fluid is supplied to perform a cooing operation, and when the temperature of the bearing chamber reaches a suitable level, the fluid supply to the bearing chamber is cut off.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a turbo compressor including: a casing having a fluid chamber for receiving a fluid from an external source; a driving unit disposed in the casing and generating a rotational force; a first compressing part installed at one side of a rotational shaft rotated according to the driving of the driving unit and first compressing the fluid; a second compressing part installed at the other side of the rotational shaft and secondly compressing the fluid compressed in the first compressing part; and a bearing cooling unit for supplying a fluid of the fluid chamber to a bearing chamber to perform a cooling operation when a temperature of the bearing chamber where the thrust bearing for supporting a load working in an axial direction of the rotational shaft is mounted is increased, and cutting off the fluid from being introduced into the bearing chamber when the temperature of the bearing chamber is maintained at a proper level.
In the turbo compressor of the present invention, the bearing cooling unit includes a supply passage formed inside the casing to allow the bearing chamber and the fluid chamber to communicate with each other; and an open-and-shut valve installed at the supply passage and opening and closing the supply passage according to an internal temperature of the bearing chamber.
In the turbo compressor of the present invention, the supply passage is penetratingly formed at a first support member which is fixed at the inner side of the casing and rotatably supports one side of the rotational shaft.
In the turbo compressor of the present invention, the open-and-shut valve includes a valve body part formed having a certain space at the supply passage, a fixed plate fixed at one side of the valve body part and having a through hole communicating with the supply passage at a center thereof; and a bi-metal positioned adhesive to one face of the fixed plate, having a plurality of through holes at its marginal portion, and being deformed according to a temperature inside the bearing chamber.
The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.